optimization

问题 Starting with code like this void lib_memset( unsigned char *dest, unsigned char c, unsigned int n) { while(n--) { *dest=c; dest++; } } using llvm as a cross compiler clang -Wall -m32 -emit-llvm -fno-builtin --target=arm-none-eabi -c lib_memset.c -o lib_memset.bc opt -std-compile-opts -strip-debug -march=arm -mcpu=mpcore -mtriple=arm-none-eabi lib_memset.bc -o lib_memset.opt.bc llc -march=arm -mcpu=mpcore -disable-simplify-libcalls lib_memset.opt.bc -o lib_memset.opt.s llc -march=arm -mcpu

问题 I have a function to optimize, say Function, in Matlab. This function depends on variables (say x) over which I want to optimize and one parameter (say, Q) which does not need to be optimized.Hence, the function Function(x,Q). In other words, I have an array of values for Q and want to find optimal x values for each Q. However, I cannot find a way how to pass those Q values when using function handle @Function in optimization function. So, my question is how to pass those Q values when using

问题 The title of this question isn't so clear, but the code and question is straightforward. Let's say I want to show my users an ad once per day. To accomplish this, every time they visit a page on my site, I check to see if a certain memcache key has any data stored on it. If so, don't show an ad. If not, store the value '1' in that key with an expiration of 86400. I can do this 2 ways: //version a $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->get($key)===false){ $memcache->set(

问题 I'm trying to optimize my C++ code. I've searched the internet on using dynamically allocated C++ arrays vs using std::vector and have generally seen a recommendation in favor of std::vector and that the difference in performance between the two is negligible. For instance here - Using arrays or std::vectors in C++, what's the performance gap?. However, I wrote some code to test the performance of iterating through an array/vector and assigning values to the elements and I generally found

问题 suppose i a have a multiplicative expression with lots of multiplicands (small expressions) expression = a*b*c*d*....*w where for example c is (x-1), d is (y**2-16), k is (x y-60)..... x,y are numbers and i know that c,d,k,j maybe zero Does the order i write the expression matters for faster evaluation? Is it better to write c d k j....*w or python will evaluate all expression no matter the order i write? 回答1: Python v2.6.5 does not check for zero values. def foo(): a = 1 b = 2 c = 0 return a

问题 While I understand that the answer to the above question is somewhat determined by your application's architecture, I'm interested mostly in very simple scenarios. Essentially, if my app is pinging every 5 seconds for changes, or every minute, around when will the data being sent to maintain the open Web Sockets connection end up being more than the amount you would waste by simple polling? Basically, I'm interested in if there's a way of quantifying how much inefficiency you incur by using

问题 I have another question regarding optimizing mysql indices for our prioritizing jBPM. The relevant indices look like this: | JBPM_TIMER | 1 | JBPM_TIMER_REVERSEPRIORITY__DUEDATE_ | 1 | REVERSEPRIORITY_ | A | 17 | NULL | NULL | YES | BTREE | | | JBPM_TIMER | 1 | JBPM_TIMER_REVERSEPRIORITY__DUEDATE_ | 2 | DUEDATE_ | A | 971894 | NULL | NULL | YES | BTREE | | | JBPM_TIMER | 1 | JBPM_TIMER_DUEDATE_ | 1 | DUEDATE_ | A | 971894 | NULL | NULL | YES | BTREE | | JBPM asks two questions when retrieving

问题 I have a function in R that I wish to maximise subject to some simple constraints in optim or constrOptim , but I'm struggling to get my head around ci and ui to fit my constraints. My function is: negexpKPI <- function(alpha,beta,spend){ -sum(alpha*(1-exp(-spend/beta))) } where alpha and beta are fixed vectors, and spend is a vector of spends c(sp1,sp2,...,sp6) which I want to vary in order to maximise the output of negexpKPI . I want to constrain spend in three different ways: 1) Min and

问题 I have a 8 sets of data of about 30,000 rows for each set, the data is the same structure just for different languages. The front end of the site will get relatively high traffic. So my question is regarding MySQL performance, if i should have a single table with one column to distinguish which set the data belongs to (i.e. coloumn "language") or create individual tables for each language set? (an explanation on why if possible would be really helpful) Thanks in advance Shadi 回答1: I would go

问题 This question already has answers here : The performance impact of using instanceof in Java (24 answers) Closed 5 years ago . I have a colleague here in my project, who is deeply against the use of instanceof operator, because it "generates a lot of overhead", what is the reason for that? Is it true? Is there another way to check the type of the Object instead of using it? Because I find it very useful in some occasions. 回答1: It does generate some overhead, combined with the subsequent